Don't know if anyone brought this up already, but there is now an updated version of the INAT FAQ. It came out a few days ago and includes the changes from the recent round of codex FAQs. It is version 5.1 as opposed to 5.0.1 and can be found on dakkadakka (http://www.dakkadakka.com/core/inat_faq.jsp).

There are some significant differences between the two, I recommend taking a look.

GK.21A.03 – Q: If a Grey Knight unit with ‘Brotherhood of Pyskers’ suffers multiple ‘Perils of the Warp’ attacks at the same time (such as being hit by several Mindstrike missiles at once) what happens? A: All the ‘Perils of the Warp’ attacks caused at the same time (from the same enemy unit’s shooting) are resolved against the Justicar/Knight of the Flame, if present. If the unit doesn’t have a Justicar/Knight of the Flame, then randomly determine a (non-character) model in the unit to suffer each ‘Perils of the Warp’ attack [clarification].